I have a uniweld CO2 regulator that I got from a guy that was using it on a keezer, but the back of the regulator is stamped "Not for Beer".
Is there any reason that a particular regulator would be unsafe?

I just received one of those for christmas. I called Uniweld and asked about that. I was told it had something to do with flow. Some people had problems with them over-pressurizing kegs and they blew up.